Reproductive biology of Citharinus citharus in Onah Lake, Asaba, Delta State of Nigeria
AbstractThe breeding cycle of Citharinus citharus was investigated from 432 specimens collected from Onah Lake, in Asaba, Delta State of Nigeria. This species formed the mainstay of the fishery resources of the lake. The reproductive biology of this species was analyzed using standard techniques. The sexes were dominated by the males in a ratio of 1:1.4 suggesting that the males probably live longer than the females. Six matured males and females each were encountered. Only four females out of this number was in the spawning stage while the remaining two females were in the spent condition. All six males encountered had their gonads in the spent condition. The size at maturity was not similar in both sexes. The females mature earlier at a standard length of 17.5cm than the males (19.0cm). The youngest spawning female had a standard length of 30.0cm and a body weight of 1310.0g while the youngest spawning male had a standard length of 32.2cm and a body weight of 899.6g. The survival of this species was guaranteed because it had a high fecundity ranging between 14,320 and 16,009. The relationships between fecundity and standard length, fecundity and corrected body weight were described. The gonado-somatic index (G.S.I) was higher in female than in male specimens throughout the period of study. This species was a total spawner with the spawning stock encountered only during heavy rains (May–July). Only one period of peak spawning was established for this species in May/June while the recruits became ready for spawning after three years.
Tropical Freshwater Biology 2003/2004 Vol. 12/13: 119-129